[Repo Assist] Fix record copy expression indentation when nested in parentheses

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Closes #2529

Root Cause

When formatting a multiline record copy expression (e.g. { r with Z = 1; X = "value" }) that is nested inside parentheses, the genMultilineRecordCopyExpr function could produce F# offside errors.

The issue is in how indentation is computed for the record fields:

1. atCurrentColumnIndent (genExpr copyExpr) writes the copy-expression identifier (r) at the current column C, temporarily setting Indent = C
2. After that call completes, Indent is restored to the outer binding body level (e.g. 4)
3. indent (IndentBy IndentSize) then computes the field indent as 4 + 4 = 8
4. When nested parens push r to column 8 as well, Z = 1 lands at the same column as r → offside error

Example before:

let b =
    (({ r with
            Z = 1        // <- same column as 'r' above! F# rejects this.
            X = "longstring value here"
    }))

Fix

Capture the column where the copy-expression identifier will be written before calling atCurrentColumnIndent. After the normal indent call, if the resulting Indent would be ≤ the copy-expression column, bump it to copyExprColumn + IndentSize. Use RestoreIndent (instead of unindent/unindent) to cleanly restore the original indent level.

Example after:

let b =
    (({ r with
            Z = 1        // <- 4 columns past 'r' ✓
            X = "longstring value here"
    }))

The fix is backward-compatible: for the common case where the copy expression is not deeply nested, Indent + IndentSize > copyExprColumn is already true and no adjustment is made.

Trade-offs

• Minimal change: only genMultilineRecordCopyExpr is modified
• Replaces onlyIf addAdditionalIndent unindent +> unindent with a single RestoreIndent oldIndent — equivalent in the common case, but correct when the indent was manually bumped

Test Status

• Build: ✅ succeeded
• Tests: ✅ 2739 passed, 7 skipped, 0 failed (added 1 new regression test)

New regression test added in AlignedMultilineBracketStyleTests.fs: record copy expression nested in parentheses should not produce offside errors

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